1. Field of the Invention
This invention relates to an image reading system, and more particularly related to an image reading system comprising an image display function in addition to an image reading feature which can be mounted satisfactorily in small electronic devices, such as portable devices and the like. Furthermore, this image reading system is applied by the user and relates to a personal authentication system which performs authentication of the person themselves.
2. Description of the Related Art
Conventionally, an image reading device which reads detailed irregular patterns and shapes, such as a fingerprint and the like, is known. The device structure of semiconductor types, those similar to electrostatic capacity reading types, reads detectable object images, such as a fingerprint, which are classified broadly by detecting electrostatic capacity based on the difference of potential produced between a detectable object (finger) and the detection sensors. A detectable object image is captured through an optical system, such as a prism, mirror or the like, and the optical device structure reads the light and dark information with photosensors arranged in a matrix form, such as in Charged-Coupled Device (CCD) or Complementary Metal Oxide Semiconductor (CMOS) sensors. With such an image reading device, an individual can be identified by comparing biological characteristic information, such as a fingerprint, and application to the termed field of “personal authentication technology” research is being extensively studied and developed.
In the device structure of the semiconductor type mentioned above, a detectable object is placed on the reading detection area which reads the detectable object image. Although the device has a benefit that it can be formed very thin and lightweight using semiconductor manufacturing technology, it has a disadvantage of being susceptible to generating static electricity damage in the detection sensor by a static electricity charge from the detectable object.
On the other hand, in an optical device structure, since an optical system intervenes between the detectable object and the photosensor, although not suitable for neither thin shaping nor weight saving, as an electrical connection state does not physically exist between both sides it is difficult to generate static electricity damage of the photosensor by the static electricity charge from the detectable object and has a benefit that the reading speed response of a fingerprint is also relatively quick.
Incidentally, in recent years the spread of portable electronic devices, such as cellular/mobile phones, notebook personal computers, Personal Digital Assistants (PDA) and the like has been remarkable. While such electronic devices are a convenience which promote communication via voice, electronic mail and the like freely or a person can move around with lot of information, these devices have the risk that personal information may be disclosed or important confidential information may be stolen. For that reason, in order to prevent disclosure and theft of such various kinds of information and to restrict access to the information concerned, in the aforementioned electronic devices there is growing public desire for mounting a personal authentication system for identifying and authenticating an individual person in the unit itself.
Here, although Charged-Coupled Device (CCD) or Complementary Metal Oxide Semiconductor (CMOS) sensors are used abundantly as photosensors for image reading devices which have an optical device mentioned above, such photosensors have a configuration formed on a semiconductor substrate as is well-known and not able to permeate light. Accordingly, when an image reading device using photosensors in the electronic device is designed and mounted with a personal authentication system, the photosensors have to be formed in a portion of the housing and the supplementary display has to be formed in another location.
However, when it is considered in as such an electronic device configuration, particularly a small portable electronic device, the size of the electronic device increased and there exists a problem in constraining the portability of a carriable electronic device. Conversely, although the size of an image reading device can be reduced to control enlargement of the overall size of the electronic device, but it then becomes difficult to read detectable object images, such as a fingerprint, satisfactorily. Therefore, there exists a problem in that stabilized personal authentication can not be performed.